1. Field of the Invention
The present invention relates to a process and an apparatus for continuous production of polycarbonates, and more particularly to a process and an apparatus to produce polycarbonates having a narrow distribution of molecular weight thereof.
2. Prior Art
Heretofore, it has been known that polycarbonates from polycarbonate oligomer can be produced in stirring tanks connected in series in batch operation. According to a most commonly used process and apparatus, tanks with a stirring device, a cooling jacket and a baffle plate are connected in series by means of a pump. After feeding a reaction mixture consisting of polycarbonate oligomer, alkaline solution of dioxy compound, catalyst, molecular weight modifier and so on through an inlet, the condensation reaction proceeds in each tank by mixing reaction mixture with blades of the stirring device. However, the prior art method mentioned above has various drawbacks. The primary shortcomings of the method are: (a) each reaction tank must be stirred continuously in order to promote reaction and to maintain a suitable temperature; (b) undesirable mechanical trouble may often occur because of the complexity of the system; (c) viscosity of the reaction mixture may become as high as 2000-4000 cp during condensation, which makes it difficult to stir the mixture in terms of the undesirable agitating heat that requires heavy coolant circulated in the jacket to relieve the heat, since it has insufficient area for heat exchanging; (d) it requires a long time to change reaction conditions to manufacture different grades of products, which results in a greater amount of off-grade products, (e) increased production is difficult; and (f) the products are such that the molecular weight distribution is not well focused and the heat-resistance and impact-resistance are not qualified enough.
This invention solves those problems which the process and apparatus disclosed by the prior art have failed to resolve.